Method for controlling an instruction memory of an embedded system

Abstract

A method for controlling an instruction memory (IM) of an embedded system. The embedded system is electrically connected to a memory device used for storing a plurality of program code segments. The embedded system includes the IM and an execution unit. The steps of the method are setting up a look-up table for recording the operation status of the IM, and determining if a specific program code segment of the program code segments has been stored in the IM or not according to the look-up table when the execution unit selects the specific program code segment to execute. If the specific program code segment has been stored in the IM, the execution unit reads the specific program code segment from the IM. If not, the execution unit loads the specific program code segment from the memory device and executes it.

1 . A method for controlling an instruction memory (IM) of an embedded system, wherein the embedded system is electrically connected to a memory device used for storing a plurality of program code segments, and the embedded system comprises: 
 the instruction memory for receiving and registering the program code segments stored in the memory device;    and    an execution unit for executing the program code segments; the method comprising the following steps:    (a) setting up a look-up table for recording an operation status of the instruction memory;    (b)selecting a specific program code segment from the program code segments and executing the specific program code segment with the execution unit;    (c) determining if the specific program code segment has been stored in the instruction memory according to the look-up table before performing step (b);    (d)reading the specific program code segment from the instruction memory to execute with the execution unit if the result of step (c) is true; and    (e)loading the specific program code segment from the memory device to execute with the execution unit if the result of step (c) is false.    
   
   
       2 . The method of  claim 1 , wherein step (e) further comprises the following step: 
 (f)storing the specific program code segment into the instruction memory and refreshing a record of the look-up table for recording that the specific program code segment has been stored in the instruction memory.    
   
   
       3 . The method of  claim 2 , wherein step (e) further comprises the following steps: 
 (g)checking if the instruction memory has enough space for storing the specific program code segment before performing step (f) to store the specific program code segment into the instruction memory;    (h)storing the specific program code segment into the instruction memory if the result of step (g) is true; and    (i)overlapping the instruction memory with the specific program code segment if the result of step (g) is false.    
   
   
       4 . The method of  claim 3 , wherein step (i) further comprises the following step: 
 (j)refreshing the look-up table to record that the specific program code segment has been stored into the instruction memory and another program code segment originally stored in the instruction memory has been erased.    
   
   
       5 . The method of  claim 1 , wherein execution of steps (a) to (e) is controlled by the execution unit.  
   
   
       6 . The method of  claim 1 , wherein the embedded system is electrically connected to a host, the host comprising a control circuit for controlling the execution of steps (a) to (e).  
   
   
       7 . The method of  claim 1 , wherein each of the program code segments comprises a plurality of instructions.  
   
   
       8 . The method of  claim 1 , wherein the execution unit is an application specific integrated circuit (ASIC).  
   
   
       9 . The method of  claim 1 , wherein the embedded system is used for encryption or decryption.  
   
   
       10 . The method of  claim 1 , wherein the look-up table is set up in the memory device.  
   
   
       11 . The method of  claim 1 , wherein the look-up table is set up in the instruction memory.